Hey guys, I'm a bit late to the party but I wanted to reply here just in case anyone in the future ends up here via Google like I just did.
So, the thing to do with third party speedos like Wahoo and Garmin is this: If you have a PLANET3 on your bike, you should simply edit the wheel cirucmference setting in the Wahoo/Garmin and set it to a value higher than regular by the same factor as your PLANET3. For example: Creo SL uses a PLANET3 with a single planet configuration which means a 3.03:1 ratio, while the same device with a dual planet setup (some people preferred having a speed limit they can reach.. I know, weird. )
has half that ratio at 1.515:1. Let's say your rear wheel circumference is 2200mm and you have a single planet config -> you would multiply 2200 by 3.03 and enter 6666 as the wheel circumference in Garmin/Wahoo. Keep in mind, the motor of the bike would still read a value of distance and speed that's 3x lower than real, but on your 3rd party device that simply uses the speed sensor and has the ability to change the wheel circumference you can use this feature to correct the speed/distance displayed to a real value while keeping the bike fully derestricted.
In fact, on some PLANET3 devices the ratio was so close to 1.6:1 with a dual planet configuration, that users who have their bikes in MPH could get a real speed displayed if they simply switched their display units to km/h. Pretty neat.
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